A possible cause of cancer is circadian disruption, the mismatch between environmental factors such as daylight hours and the intake of food with our ritmos circadianos endogenous. Until now it was known that regular physical activity throughout life can reduce the risk of cancer. This protective effect could be more beneficial when physical activity is done in the morning, according to a new study coordinated by the Barcelona Institute of Global Health (ISGlobal) together with the Department of Epidemiology of the Medical University of Vienna.
Most of the research on circadian disruption and cancer risk focused on night work. Recent studies suggest that exposure to light at night and dining out late can increase the risk of cancer. However, as of yet, it is unknown whether the timing of physical activity could influence cancer risk through circadian disruption.
To address this question, the scientific team analyzed the effect of time of day to perform recreational physical activity on the risk of breast and prostate cancer in a population study of cases and controls. For this, it was hypothesized that the beneficial effect of longer physical activity to reduce the risk of cancer could be stronger when performed in the morning. They were based on the results of an experimental study that showed that physical activity in the afternoon and evening can delay melatonin production, a hormone produced mainly at night and with known anti-cancer properties.
The analysis included 2,795 people of the multicase-control study (MCC-Spain) in Spain. The researchers found that the beneficial effect of physical activity – the longest carried out throughout life – in reducing the risk of breast and prostate cancer was stronger when the activity was carried out regularly in the morning (between 8 and 10). In men, the effect was equally strong also for night activity (between 19 and 23).
The results did not change when considering the most strenuous time of physical activity. The effects differed according to the chronotypes, the preference for sleeping and being active at a certain time of the day. Early morning activity (between 8 and 10) seemed especially protective for late chronotypes, people who generally prefer to be active at night.
In the article, published in International magazine Journal of Cancer, epidemiologists analyze how physical activity can influence circadian rhythms and suggest possible biological mechanisms (for example, the alteration of the production of melatonin and sex hormones, the metabolism of nutrients, etc.).
In general, the findings of this study indicate that “the time of day when physical activity is performed is an important aspect that can enhance its protective effect on the risk of cancer “, highlights Manolis Kogevinas, researcher, who coordinated the study.
“These results, if confirmed, may improve current recommendations for physical activity for cancer prevention. What is clear is that everyone can reduce their risk of cancer simply by doing a moderate physical activity for at least 150 minutes a week“, Add.